Monday, January 16, 2012

Cold week ahead.. moderating temperatures with some snow by the weekend.

A large dome of arctic air will be flooding over the Prairies this week, bringing the coldest weather of the season so far to southern MB. Temperatures this week will likely stay below the -20C mark all week, with the season's first -30C readings predicted for Thursday and Friday mornings. A weak clipper system will bring some clouds and light snow to the RRV Tuesday night into Wednesday morning, with a dusting to 2 cm possible. Other than that, generally clear and cold weather is expected this week. A moderating trend is expected by next weekend along with a good chance of more snow. Until then, get ready for some typical Prairie mid-winter cold weather for the next few days..

For additional details on this week's deep freeze and other weather stories, check the A Weather Moment weather blog.. another local website with insightful analysis and commentary on southern MB weather.

Very cold day today across southern MB and southern SK.. a high of only -23C in Winnipeg today, while southern SK and central MB barely made it much above -30C. Clouds and some light snow moving in tonight will prevent temps from plummeting too much tonight.. in fact temps may even rise a bit overnight. Looks like a cm or two possible with this area of light snow moving in. I see visibilities have dropped to 1 mile or less in southern SK with this system. Then we clear out and tank Wednesday night into Thursday with our first -30C of the season by Thu am.

What's odd is that people think this is unusually cold.. when in fact, it's quite a normal Arctic outbreak for the Prairies. What's unusual is that it hasn't happened all winter yet! Stay warm!

About 1 cm of fine powdery snow overnight.. Radar and sfc obs indicate light snow still falling all the way to the SK border so we'll be in this stuff all day. Not much additional accumulations expected.. maybe another 0.5-1 cm. Certainly has made roads very slippery. I've noticed crews have laid lots of sand everywhere which will help traction.

The fine snow, cold air and exhaust fumes makes it look and feel like Siberia out there! Bundle up comrades!

Some near -40C temperature readings over northern Interlake this morning including -37.7C at Berens River and -39.5C at Mafeking (between Swan River and The Pas) These are actual temperatures, not wind chill.

Will likely see our first -30C temps in Winnipeg overnight as skies clear behind this clipper. Light NW flow will veer to the SW overnight which will likely prevent the airport from bottoming out like they can with a NW flow all night.. but certainly -30 to -33C possible especially outside the perimeter.

Wind chill warnings will likely be extended across all of southern MB by late afternoon including Winnipeg. Wind chills likely around -40 to -45 overnight tonight into Thursday morning across Winnipeg/RRV. (temperatures of -30 to -35C with a 15-20 km/h wind)

I'm sure me or someone has asked you this question before, but I forgot, and need to put this to rest!!!

When you have your car parked outside and is exposed to the wind and the windchill temperature is-40 C outside, does it have any effect on whether or not the car will start due to the windchill temperature??? I heard so many explanations on the interent some saying that only air temperature matters, while others say the windchill will cool the car down more quickly!!!

@Daryl: I noticed that too, I think somehow the dew point got reported as the temperature.

@Daniel: the temperature is what matters; even in a 100km/h wind your car will never get colder than the temperature. Wind can help cool things down quicker, as it wicks heat away from the surface of the object, but ultimately it's the temperature that will take it's toll on your battery and oil (which, if you think about it, are pretty sheltered from the wind).

Brad.. no problem. I can't always post updates as much as I'd like, so it's good to have another site to keep the masses out there informed!

daniel.. as Brad explained, it's the temperature that matters. Remember, wind chill is an equivalent cooling rate, not a temperature. A wind chill of -40 merely means that objects will cool off at the same rate as if the air temperature was -40C. However, those objects can never drop below the actual air temperature. So if it's -20C with a -40 windchill, it just means the battery will cool off to -20C more rapidly than if the wind was light. But it will never drop below -20C.

Another thing about wind chill.. you need wind to really make a difference. A wind chill of -45 with a 30 km/h wind feels a lot worse than a wind chill of -45 with a 5 km/h wind. The wind is what blows away the thin but effective insulating layer of warm air surrounding your skin. Once you lose that, you feel much colder and frostbite becomes a bigger risk. If the wind is only 5 km/h, then that layer of warm air over your body stays more intact, and you don't feel as cold. That's why I'm dead set against advertising wind chills if the wind speed is below 15 km/h.. the minimum wind speed for losing that insulating layer of warm air around your skin.

Interesting.. on the IR satellite loop, you can see the coldest places in southern MB over the Interlake and SE MB east the RRV where the IR return is the brightest. Off to our west, the westerly downslope flow is actually making things "milder" (i.e, not as cold) over the western RRV and downslope areas of the Riding Mtns. This "warmer" air shows up as a darker area on the IR loop - looks like low cloud but it's actually just warmer air since skies are clear. If that's the case, then areas north and east of the Red River will be the coldest spots tonight, while areas over the western RRV won't be as cold.

Note that the temperature at my site plunged to -29.5C at 7:20 pm when winds were light, but then rose to -27C by 8 pm when the westerly winds picked up.

The light west winds kept our temperature up a little bit; the coldest we got here in St. Bonifice overnight was -27.6°C. Also, closer to the core of the city, we never experienced that -30°C slump yesterday evening like Rob did, who is closer to the edge of the city.

Really shows that sometimes, especially in extremely cold weather, a temperature -range- for a city is probably a better forecast than a single number.

That or get rid of the numbers and adopt words...

Today: Sunny. Cold.Tonight: Clear. A bit of wind. Really cold.Tomorrow: Not much better.

"It was so cold, I saw a lawyer with his hands in his own pockets." LOL!

But not as cold as it could have been. We never hit the -30C mark last night, with the Winnipeg airport hitting a low of "only" -28.9C last evening, then staying steady at -28C the rest of the night thanks to that westerly breeze. Coldest spots last night were north and east of Winnipeg with lows of -33C in Gimli, Pinawa and Great Falls.

Forecast calls for another -30ish low tonight.. winds are lighter tonight so may hit it this time.

Looks like we'll get some light snow developing Saturday ahead of a warm front that will be ushering in milder air by Sunday. We may see a cm or two out of it before the area of snow moves into the Interlake. There will be some brisk southeast winds Saturday gusting to 50 km/h by afternoon, so windchills will be significant, although not warning levels.

Sunday we get milder and winds ar elighter, so it will definitely be the nicer of the two days this weekend. But we have an inverted trof over us which will likely be giving us some snow, perhaps 2-5 cm if you believe some of the model guidance. That should taper off Sunday night with slightly colder and drier weather for Monday.

Boy there's some big differences among the models for tomorrow.. The NAM keeps pushing the snow further and further north, with significant accumulations tomorrow, including WPG. Meanwhile, the GLB keeps it well to the south with just a skiff of snow. While the GFS shows just the southeast tip of MB seeing heavy snow in a narrow band with WPG right on the edge.

yes, models have a pretty sharp drop off in snowfall between the US border and Winnipeg. The cutoff is marked by a deformation boundary that will set up around the upper low moving through the Dakotas. Areas northwest of this boundary will receive much less snow, with higher amounts to the south and east. If this defn zone is not predicted correctly, (and it only needs to be off 60 miles or so) then the heavier snow will push further north and west and affect Winnipeg. Right now, I'm sticking with my initial estimate of about 2-5 cm for Winnipeg, with heavier amounts of 5-10 cm south and east of the city. If that DZ sets up further NW (which it can often do in these inverted trof setups), then Winnipeg could see more snow tomorrow.